Conventionally, a device enabling naked-eye viewing of multiple-parallax video, such as stereoscopic video, involves a display device such as a liquid-crystal display panel (hereinafter, LCD panel) or a plasma display panel (hereinafter, PDP) having a parallax barrier, a lenticular lens, or the like (i.e., a spectral dispersion unit) disposed on a viewer-facing side thereof. Accordingly, light from left-view and right-view images displayed by the display device is split into left and right components to produce the stereoscopic images.
FIG. 38 illustrates the principles of a stereoscopic video display device using a parallax barrier without 3D glasses, as disclosed by Non-Patent Literature 1. As shown, a parallax barrier 2 is arranged to face a user 4 of a video display panel 1. The video display panel 1 has vertically-aligned left-view pixels L and likewise vertically-aligned right-view pixels R, disposed in alternating columns. Also, the parallax barrier 2 has vertically-oriented slit-shaped apertures 2a formed in plurality thereon, the apertures 2a being separated by screening portions 2b extending vertically between the apertures 2a. With the left-eye image arranged in the left-view pixels L and the right-eye image arranged in the right-view pixels R at an appropriate binocular disparity, the viewer perceives a single stereoscopic image. A viewer wishing to view the stereoscopic image having their head at a proper position (i.e., a forward viewing position) has left-view images 3L reach their left eye 4L via the apertures 2a, and has right-view images 3R reach their right eye 4R via the apertures 2a, such that the user perceives stereoscopic images. Here, the left eye 4L is prevented from seeing right-view image light by the screening portion 2b, and the right eye 4R is likewise prevented from seeing left-view image light by the screening portion 2b. Accordingly, the viewer 4 is able to view naked-eye stereoscopic video.
However, in such a stereoscopic video display device, an interference pattern (i.e., a Moiré pattern) is produced between a pattern of the parallax barrier 2 and a pixel pattern of the video display panel 1 in the plasma display device or the like. This Moiré pattern varies according to the shape and width of the apertures in the parallax barrier. Typically, a region termed a black matrix is arranged between each RGB sub-pixel in order to cancel any colour mixing. Such a region is present in LCD televisions and in PDPs. In addition to the black matrix between sub-pixels, auxiliary electrodes and the like are disposed over the sub-pixels. As such, the black matrix and auxiliary electrodes are visible through the slits in the parallax barrier and produce a difference in brightness between apertures having a higher or lower proportion of black matrix and auxiliary electrode portions visible therethrough. As a result, uneven screen brilliance (i.e., a Moiré pattern) is produced and greatly diminishes image quality.
FIGS. 39A and 39B illustrate examples of Moiré patterns perceived when the full screen of the display is white, with FIG. 39A showing a situation where the display screen has step barriers formed of slits in step form, and FIG. 39B showing a situation where the display screen has oblique slant barriers formed therein. Here, the horizontal width of the aperture slits is equivalent to the width of the sub-pixels (i.e., aperture ratio×1). For a step barrier as shown in FIG. 39A, the horizontal and vertical area of pixels visible through the step barrier slits and the ratio of combination thereof with black matrix portions varies according to viewing position, thus increasing the tendency of a lattice-like Moiré pattern being produced. For a slant barrier as shown in FIG. 39B, the variation in pixel area is smaller than the equivalent variation for the step barrier, regardless of the positional relationships involved. Thus, the Moiré pattern contrast tends to be less than occurs with the step barrier. Particularly, the Moiré pattern is less perceptible in the horizontal direction. However, the Moiré pattern is nevertheless present for both types of pattern, and causes perceptible reduction in image quality during 2D, rather than 3D, viewing. In order to eliminate the Moiré pattern during 3D display, Patent Literature 1 proposes a method of alternating, at a predetermined angle, between a first plate having a pattern formed at a first periodicity and a second plate having a pattern formed at a second periodicity. FIG. 40 schematically represents such an approach, indicating the barrier pattern being slanted by an angle within 20° to 30° relative to the pixels, in order to diminish the Moiré pattern.
Also, as shown in FIG. 41, a tooth-shaped vertical stripe pattern having a barrier pitch of ½ is disclosed (Patent Literature 2). In such a case, the pixels and the black matrix are greatly averaged out. Aside from this shape, FIG. 42 discloses zig-zag and curved patterns that are also applicable (Patent Literature 3).